A Novel Current Differential Relaying Scheme for Transmission Line Protection

This paper proposes a latest current differential protection technique for a three-phase power transmission system. A protective relay is designed for recognition and classification of faults in a three-phase transmission line using three-phase fault currents measured synchronously at two- buses which are located at two sides of the transmission line. The designed protective relay is based on the computation of the differential approximate coefficients of wavelet transform (DACWT) of three-phase fault currents which is utilized to recognize the fault, classify the faulty phase, and discriminate the external and internal faults in a transmission line. The designed protective relay has been tested comprehensively using MATLAB with modification of fault parameters. The performance of the protective relay is verified for symmetrical faults, unsymmetrical faults, external faults, low-impedance faults, and high-impedance faults. Moreover, the sensitivity of the protective relay is also ensured when the transmission line is connected with a three-phase power source at one-end only. Simulation outcomes authenticate the effectiveness of protective relay as the faults are recognized and the faulty phases are categorized in near about half-cycle from the instigation of fault.